Instrument developement proposal: Development of a condensation particle detection system (COPAS) with multiple inlets for implementation on stratospheric aircraft or balloons

Projektdetails

Gesamtkosten:

EU-Beitrag:

Koordiniert in:

Thema(en):

Finanzierungsprogramm:

CSC - Cost-sharing contracts

Ziel

Objective of this project in addition to the instrument design and construction is to have the COPAS instrument implemented on the Geophysika stratospheric research aircraft thus completing the Geophysika payload for aerosol measurements. During the Geophysika flights in connection with the Airborne Polar Experiment (APE) in the period from late 1996 until 1998 the instrument is utilised to obtain in situ stratospheric aerosol measurements with special emphasis on the lee wave mountain polar stratospheric clouds over the Scandinavian Alps and the Urals, and the mid latitude stratosphere. The detailed scientific objectives are to: - detect and count (not size) the smallest stratospheric particles in the important particle size range from 0.01 fm to 0.4 fm. - measure the number concentration of the smallest aerosol particles to characterise the microphysical processes of the formation and lifecycle of polar stratospheric clouds. - detect freshly nucleated aerosol particles from gas-to-particle conversion as basis of the Junge layer formation. - improve accuracy of total aerosol surface and volume measurements especially in volcanically quiescent periods. Most other airborne stratospheric particle instruments do not detect particles smaller than 0.01 fm and this small particle fraction is not included in total surface measurements. - obtain information about nonvolatile residues of the particles, i.e., address the homogeneous vs. heterogeneous nucleation issue for polar stratospheric cloud formation and for the formation of the stratospheric background aerosol. - separate PSC I from PSC II particles while enhancing PSC II particle concentration in the sample. Thus better particle detection counting statistics, an important issue for short events like lee wave PSCs. - measure the particles generated in aircraft exhaust plumes during contrail crossings.

The proposed instrument consists of a condensation particle counter capable of optically detecting particles with size diameters from 10 nanometers to 10 micrometers after pre-treating them in three different sampling inlets. The aerosol particles are only counted (not sized), which renders three total particle number concentrations according to the pre-treatment in the inlets. The design contains: - one inlet where the incoming aerosol is heated to 200-300 C before being admitted to the condensation particle counter, - a second inlet which forms a so called Counterflow Virtual Impactor (CVI) where -coarsely described- a counterflow principle admits only aerosol particles larger than a certain (adjustable) size to enter the condensation particle counter, - a third, passive inlet where the aerosol is not treated at all before coming into the condensation particle counter for comparison with the results of the other channels.